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Intro with R90/6 questions

Hi everyone. I've been eyeing airheads for some time now (the bikes, not the blondes) and the R90/6 has been on my short list of bikes. One came available locally and along with my binge-researching I figured you folks could help me out with bike basics. (yes I've also been searching the forum(s) and other sites for info). I own two Guzzis (a newer V7 and an '84 V65sp), am capable of doing my own work up to a point and am a quick learner past that comfort zone, which is part of the fun of ownership for me. I test ride motorcycles and scooters at a local shop (both new bikes and service bikes) so I've ridden a crazy range of different makes and models, old and new....but I don't have much experience with BMWs, airheads in particular.

The R90/6 I'm looking at is a '74 and is in good shape. Cosmetics are great, new tires, new fluids (all), most original bits there. Other notes:

-Starts right up and settles into easy idle immediately.

-The dual choke lever is missing so the current owner manually chokes each carb if need be, though it didn't require choke on its cold start the other day. I would want to buy two new choke cable and a new lever (or I've seen the "rigged" choke pulls as well).

-Carbs (Bing) looked very clean, though upon shutoff the right carb dropped gas from the bowl for a few seconds. It surprised me when i saw the drip, though the owner was unconcerned, saying it happens only sometimes if the petcock isn't shut off or it's on its side stand after shutoff...and I've read a few people online saying the same thing. It seemed excessive to me though and I'd bet a float/o-ring type fix would erase it?

-Odometer is broken at about 87k. I've read this is common and possibly not a crazy hard fix.

-It does still have the kick start, but obviously is well over the fabled 1974 30k or so gearbox eruption. I was told a previous owner disassembled and went through "everything", making a few changes (wiring, dual plugs, etc) but I can't be sure if he did any transmission changes...even just detent spring. If it still has the kick does that ALWAYS mean it still has the original '74 bits inside?

-Dual plug heads as I mentioned (and btw if someone could give me an elementary explanation of how this worked for R90s I'd love it)

-single disc up front...yeah not great

-doesn't seem to "clunk" through gears as I've read people mention. Seemed smoother than I expected.

So that's it off the top of my head. Any thoughts people could ad to my comments, or just general airhead things I may not realize would be appreciated. I know price ranges for these are all over the map, especially on Ebay, so I'm not so hung up on that.

Welcome to the forum! Sounds like you've done a bit of homework and know what you're stepping into. The '74 transmissions can be problematic although you'll get a range of stories...some go many many miles with them. The kick start should be used sparingly. Snowbum has a recommended mod to keep the idler gear from falling off inside.

Check the link in my signature line for a range of websites and other links that might be helpful.

I've owned two bikes (74R90S and 78R100RS) with dual plugs. When I got the R90 the bottom plug was not connected. I sold the bike to a friend that installed a Dyna III and connected the bottom plug. The pinging that I had with it went away, it started better, and ran better. I do not fully understand it, but it is found on other bikes such as my old 2004 R1100S. Since that bike engine was a fairly modern design, with an improved version of the same engine used on the R1100RT's (I've also owned two of those). The R1100S had dual plugs, and did not surge like the single plug R1100RT's are known for.

One follow up question, and really my biggest concern, is what are my chances of having to overhaul the gear box down the road? So we're assuming the bike has more than 85k miles on it, currently runs and shifts well, still has the kick starter (which by the way the current owner uses from time to time and says works perfectly. I winced when he said that, but then again with so many miles on it, if it doesn't seem to be stubborn...does it matter?).

Is there such as thing as "well if it were going to go boom it would have already"? Or are the '74s always a ticking time bomb when it comes to the gearbox?

I wouldn't worry that much about the box. Keep an ear on it, look at the fuzz on the drain plug...anything more than fuzz and you're headed for a rebuild. You could check the "feel" of the bearings by rotating the output flange while in gear and the clutch disengaging from the engine...I think you can then turn every gear. Should be smooth with no binding.

I don't think there's a rash of gear box failures...with decent care and oil changes, they last many many thousands of miles, daresay 100s of thousands of miles.

I've got a 74 R90/6 and had to have gearbox rebuilt but it was due to sitting unused 18,900 miles in 38 years left gears pitted. If bike has a decent maint history then I wouldn't sweat it. I occasionally kick start mine just to prove I can, but it's maybe once a year. (Gives me a good idea of the state of tune). Do you have the aluminum turn signals? Really like those!

I have a 1974 R90/6 that I have owned for awhile and (mostly) thoroughly enjoyed. Every model/year has pros/cons (my opinion), so hard to find perfection. The '74 is unique in that it still has some /5 bits (controls, metal turn signals, kick start) some new /6 bits, and a few things completely unique. I like this aspect.

But, it is getting near 40, so no matter how well it was maintained, I think you have to be up for an ongoing repairs program which hopefully you can attend to during the winter months. Good news is that parts (new and used) are available as are expert advice and professional services. You know from pricing research in prep for purchasing, you won't get back what you spend on it, but that isn't what thesemachines are about.

You know from pricing research in prep for purchasing, you won't get back what you spend on it, but that isn't what thesemachines are about.

So true, and completely understood. My ultimate goal, obviously, is owning two wheeled machines I can enjoy, both on the road and in the garage. Guzzi sucked me in for that very reason, as I find them easy(er) to work on and great fun to ride...and I feel a similar pull from this R90/6.

Quick focus on that carb fuel drip I mentioned....I'm not familiar at all yet with Bing carbs, mainly just Dell'Orto....anyone else have experience with this kind of drip? I thought it odd.

Quick focus on that carb fuel drip I mentioned....I'm not familiar at all yet with Bing carbs, mainly just Dell'Orto....anyone else have experience with this kind of drip? I thought it odd.

You need to measure how much fuel is in the float bowl and set the floats to the proper depth of floatation......sounds complicated but nothing really......do a search in "airheads" for float bowl depth.........lots of discussion about this. Then another cause could be that the foam floats have become "soaked" and sink a bit due to their change in weight...........Then again, if it's on the left side and when you put it on the sidestand and you have a marginal, 'to much fue in the bowll" situation there could and will be a bit of a drip.........lol......then again, it could be a fuel hose leaking on an on and off basis........
Usually just the float level; but often times it will be the floats are saturated.......NO BIGGY either way......God bless.....Dennis

Could be something as simple as a bit of grit between the float needle and the seat that you can flush out by taking off the bowl and letting it run a bit. Could be the float is breaking down and saturated so it isn't floating to shut off the flow of gas. Could be the float needle needs replacing. Could be the cork bowl gasket is torn.

Plus a couple of other simple things that others will chime in on. Should be easy to fix.

Individual parts plus rebuild kits for the carbs (diaphrams, floats, o-rings, gaskets, needles, jets) are all available from BMW and will be on your "to do list" along with the rubber washer and screen for the petcocks (and new fuel line while you are at it!).

Yes to the last two posts...

...and I have also had mine drip a bit when the whole carb is turned too much to that side. Know what I mean? Because you can rotate that carb by loosening the hose clamps. Think it looks better to have the carbs (top) angled in, but may cause dribbles.

I have also had mine leak; pulled off and emptied the bowls; let the float hang and dry out for a couple of days - and the problem was solved. Repairs by tweaking the mechanisms. Good luck, Sir!

Picked her up this morning. I didn't have enough time on her today to suit me, but I'm going to love having this bike. So many Guzzi similarities and yet so unique...it's a whole new (cool) world. Thanks all for the advice so far.

Pics attached are of the bike after I picked her up and one my daughter snuck of me driving to work.

Absolutely gorgeous machine. Mine is finally to the stage where I can safely ride it so Sunday afternoon I took a short ride...176 miles. You and I are starting our adventures at the same time and I look forward to further postings. My left carb leaks as well, but I have a bad float bowl gasket. I should get a set in from MAX BMW tomorrow.